U.S. patent number 4,094,306 [Application Number 05/681,037] was granted by the patent office on 1978-06-13 for apparatus for ultrasonic examination.
This patent grant is currently assigned to The Commonwealth of Australia, c/o The Department of Health. Invention is credited to George Kossoff.
United States Patent |
4,094,306 |
Kossoff |
June 13, 1978 |
Apparatus for ultrasonic examination
Abstract
Apparatus for the pulse-echo ultrasonic examination of an object
comprised of transducer means for transmitting pulses of ultrasonic
energy and receiving reflected echoes of said pulses immersed in a
coupling medium contained within a housing, the pulses being
transmitted and echoes received through an aperture in the housing
which may be covered with a flexible coupling membrane and the
housing including a storage header tank open to the atmosphere to
maintain the pressure to the coupling medium on the membrane
constant during flexing of the membrane.
Inventors: |
Kossoff; George (Northbridge,
AU) |
Assignee: |
The Commonwealth of Australia, c/o
The Department of Health (Phillip, AU)
|
Family
ID: |
3691973 |
Appl.
No.: |
05/681,037 |
Filed: |
April 28, 1976 |
Foreign Application Priority Data
Current U.S.
Class: |
73/607; 128/915;
73/620; 601/2 |
Current CPC
Class: |
G01N
29/223 (20130101); G01N 29/262 (20130101); A61B
8/406 (20130101); G01N 29/0609 (20130101); G01N
29/06 (20130101); A61B 8/4209 (20130101); A61B
8/0825 (20130101); Y10S 128/915 (20130101) |
Current International
Class: |
A61B
8/08 (20060101); G01N 29/06 (20060101); G01N
29/22 (20060101); G01N 29/26 (20060101); A61B
010/00 () |
Field of
Search: |
;128/2V,2.5Z,24A
;73/67.8S |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Howell; Kyle L.
Claims
The claims defining the invention are as follows:
1. Apparatus for use in the ultrasonic examination of an object,
said apparatus comprising:
a housing adapted to be filled with a liquid coupling medium, said
housing having a substantially horizontal upper surface and being
provided with an aperture in said surface;
a flexible coupling membrane covering said aperture in a
liquidtight seal;
transducer means contained within said housing and adapted to be
immersed in said coupling medium, said transducer means comprising
means for transmitting pulses of ultrasonic energy through said
aperture into an object positioned adjacent said aperture and means
for receiving echoes of said pulses of ultrasonic energy reflected
through said aperture by acoustic impedance discontinuities within
the object; and
an open storage header tank for said liquid coupling medium in
communication with said housing and the atmosphere to maintain the
pressure of said coupling membrane constant during flexing of the
membrane.
2. Apparatus as defined in claim 1 wherein said transducer means
comprises a plurality of transducers mounted in an arm, said arm
being mounted within the housing by a supporting mechanism for
movement thereof with respect to the object.
3. Apparatus as defined in claim 2, wherein said arm is curved
about a point spaced a predetermined distance above said
membrane.
4. Apparatus as defined in claim 2, wherein said supporting
mechanism includes means to move said arm towards and away from
said object, means to move said arm longitudinally and transversely
with respect to an axis of said object, and means to rotate and
tilt said arm with respect to said object.
5. Apparatus as defined in claim 2 wherein each transducer of said
plurality of transducers is mounted in said arm for pivotal
movement in the plane of the arm, and said transducers are
mechanically linked for simultaneous movement.
Description
This invention relates to the technique of ultrasonic echoscopy of
objects and in particular to means for decreasing the time required
for examination of an object using the pulse-echo ultrasonic
technique and for improving the clarity and hence the utility of
the examination results. It is particularly, but not solely,
directed to the use of this technique in medical diagnostic
examination.
Ultrasonic echoscopy provides information about an examined object
which may be displayed in the form of an ultrasonic echogram. Such
an echogram consists of a display of acoustic impedance
discontinuities or reflecting surfaces in the object. It is
obtained by directing a short pulse of ultrasonic energy, typically
in the 1-30 MHz frequency range, into the examined object where any
acoustic impedance discontinuities in the object reflect and return
some of the energy in the form of an echo. This echo is received,
converted into an electric signal and displayed as an echogram on a
cathode ray oscilloscope, a film, a chart or the like.
The echogram may constitute either a one dimensional or a two
dimensional representation and in both cases the information is
contained in the position and magnitude of the echo displayed. In a
one dimensional display, the position along a base line is used to
indicate the distance to the reflecting surface whilst the
magnitude of the echo is displayed for example as a deflection of
the base line "A mode" or as an intensity change "B mode". In a two
dimensional display, the position along a base line is used to
indicate the distance to the reflecting surface as in a one
dimensional display, and the direction of the base line is used to
represent the direction of propagation of the acoustic energy. The
two dimensional display is obtained by changing this direction of
propagation of the acoustic energy and by instituting a similar but
not necessarily identical movement of the base line of the display.
The magnitude of the echo is displayed as for a one dimensional
display, for example, as a deflection of the base line or as an
intensity change.
The technique of ultrasonic echoscopy is used in medical diagnosis
to obtain information about the anatomy of patients. The
application of this technique is now widely investigated and is
described, for example, by D.E. Robinson in Proceedings of the
Institution of Radio and Electronics Engineers Australia, Vol. 31,
No. 11, pages 385 - 392, November, 1970 : "The Application of
Ultrasound in Medical Diagnosis". As pointed out in this article,
ultrasonic echoscopy may be used to produce displays resembling
anatomical cross-sections which have proved clinically useful when
the desired information concerns physical dimensions, shapes of
organs or structures or the like. Ultrasonic echography has proved
of particular value as a diagnostic aid in the abdomen and pregnant
uterus, eye, breast, brain, lung, kidney, liver and heart, these
being areas of soft tissue with little bone and air. In general,
the technique is considered to complement other techniques to
provide a more complete picture of the patient's condition,
however, particularly in pregnancies, ultrasonic echoscopy may be
useful in place of X-rays where the latter may not give sufficient
information or may be dangerous. In medical use, a pulse of
ultrasonic energy is transmitted into a patient in a known
direction and echoes are received from reflecting surfaces within
the body. The time delay between a transmitted pulse and the
received echo depends on the distance from the transmitter to the
reflecting surface and the distance information so obtained may be
displayed in a suitable way for interpretation and clinical use as
a one dimensional range reading or as a two dimensional cross
section as previously described.
In one presently known form of ultrasonic diagnostic examination, a
single transducer is used and it is physically moved to various
positions around the patient. At each of these positions the beam
is swept with an oscillatory motion while constrained to remain
within a single plane by mechanical oscillation of the transducer,
to obtain the required scan pattern. By the use of suitable
deflection circuits, for example, in a cathode ray display tube, a
line is caused to follow the motions of the beam axis and echoes
within the part examined are thus displayed in their correct
geometrical positions. By way of example, for transverse sections,
the transducer may be moved horizontally in a 150.degree. arc
around a patient who is substantially erect while undergoing .+-.
15.degree. oscillations and for longitudinal sections the
transducer may be moved vertically while undergoing .+-. 30.degree.
oscillations.
It has, however, been found that in such systems where the
transducer is physical moved around the patient this movement leads
to a limitation on the examination time of between ten and twenty
seconds for each cross-sectional visualization due to mechanical
inertia and, in the case where the transducer is coupled to the
patient via a coupling medium such as water, the generation of
turbulance by the transducer when it moves quickly in the coupling
medium.
Several alternative forms of ultrasonic examination equipment have
been devised which will avoid the limitations discussed above and
thus enable a speeding up of the time required for each
cross-sectional visualization. It will be apparent that a reduction
in examination time of a patient will lead to a technical
improvement in the resultant echograms as the effects of movement
of the part under examination will be reduced. In addition, a
reduction in examination time of a patient will have the economic
advantage that more cross-sectional visualization and hence more
examinations will be able to be performed in a given time.
In the currently used two dimensional B mode systems of ultrasonic
examination, a single transducer is either mechanically driven or
manually operated to obtain an echogram. To enable examination of a
region of interest, for example of a patient, the plane of scan is
adjusted as required, an echogram obtained in that plane, and then
the plane of scan moved, and so on, usually in such a way as to
examine parallel sections of the region of interest. As each
cross-section visualization using the known systems requires from
ten to twenty seconds, the entire examination may take up to half
an hour or so. Such a long examination time is undesirable for a
number of reasons. Firstly, there can be considerable movement
during the examination period, particularly of the fetus in a
pregnant uterus, blurring individual echograms and causing
difficulty in interpreting a full set of cross-sectional
visualization over a region of interest. Furthermore, a prolonged
examination is often not possible or is at least most undesirable
when the technique is used in the examination of sick patients. Of
course, a lengthy examination time precludes the use of the
technique as a screening test, and the reduced throughput of
patients has an obviously deleterious effect on the economics of
the technique.
It is therefore an object of the present invention to provide
apparatus for ultrasonic examination of an object by the pulse-echo
technique which is capable of performing a complete ultrasonic
examination in a time considerably less than that possible at
present. As will be appreciated from the above, any reduction of
the time necessary for the examination will have the further
benefit that the quality of the echograms which are obtained will
be improved since the effects of patient movement will be
reduced.
According to the present invention there is provided apparatus for
the ultrasonic examination of an object comprising a housing
enclosing a coupling medium, said housing being provided with an
aperture therein, and transducer means contained within said
housing and immersed in said coupling medium, said transducer means
comprising means for transmitting pulses of ultrasonic energy
through said aperture into the object and means for receiving
echoes of said pulses of ultrasonic energy reflected through said
aperture by acoustic impedance discontinuities within the
object.
Preferably, the housing consists of a bath filled with water as
coupling medium. The aperture is provided in the top of the bath
which otherwise completely encloses the coupling medium.
Preferably, a flexible coupling membrane such as a polythene
membrane is provided to seal the aperture so as to ensure
satisfactory contact between the coupling medium and the object
such as a patient to be examined without loss of the coupling
medium through the aperture. In one convenient arrangement
particularly suitable for medical diagnostic examination, the bath
is constructed in the form of a couch upon which a patient may be
positioned with the body region to be examined over and in contact
with the coupling membrane. Preferably also, the coupling medium is
temperature controlled. Whilst the use of the flexible coupling
membrane as described above is preferred as a matter of
convenience, particularly where a large number of patients are to
be examined, it will be apparent that use of this membrane may also
be dispensed with thereby allowing direct contact of the coupling
medium with the patient's skin.
As previously described, in accordance with the present invention
the transducer means is immersed in the coupling medium contained
within the housing. In known ultrasonic examination systems,
coupling from the transducer to the patient has been achieved
either by skin contact or by use of, for example, a water delay
bath. Use of a water delay bath is recognised as introducing
possible ambiguities due to multiple reflection, although these may
be avoided by so arranging the system that the distance between the
transducer and the skin surface of the patient is greater than the
largest depth of penetration to be used. Nevertheless, while skin
contact systems in general result in greater comfort for the
patient, the resulting echograms are of less clarity, and the use
of water delay bath provides better quality echograms. The present
invention provides apparatus whereby these better quality echograms
may be conveniently achieved.
In order to obtain good coupling between the transducer means and
the flexible coupling membrane, or skin surface of the patient, in
accordance with the present invention the housing is filled with
the coupling medium and preferably the housing is provided with a
header tank to ensure that the housing remains filled during
flexing of the membrane, for example during positioning of the
patient on the apparatus. Fluid pressure exerted by coupling medium
stored in the header tank maintains pressure on the coupling
membrane also, thereby helping to maintain close contact between
the flexible membrane and the skin of the patient.
In a particularly important aspect of the present invention, the
transducer means comprises a plurality of transducers mounted in a
single arm, the arm being mounted within the housing by a
supporting mechanism for movement thereof with respect to the
object to be examined to facilitate examination thereof in any
desired plane. Preferably, this supporting mechanism provides
movement in the "x", "y" and "z" directions with respect to the
object and also provides for rotation and tilting of the arm with
respect to the object, thereby allowing focusing of the transducers
of the arm on the desired region of the object and scanning in any
desired plane. Preferably also, the arm supporting the transducers
is curved thereby enabling a degree of mechanical focusing of the
transducers at a point within the object to be examined. The curve
of the arm may be circular, however linear arms or other non-linear
arms may be used if desired.
The use of a plurality of transducers has been found to enable a
speeding up of the time required for each cross-sectional
visualization. In a typical operation the transducers are spatially
positioned in a single plane relative to each other and to the
object under examination as by mounting in an arm described above
and the beam from each transducer is steered to a plurality of
angular directions in this plane, for example by oscillation of the
transducers in the plane of the arm. The transducers may than be
energizing sequentially, the time of energizing each of the
transducers being set so that the whole set of transducers is
energized before the appropriate beam from each transducer has
moved a significant distance. In this way an entire scanned
crosssection may be formed in one cycle of the transducers.
Oscillatory motion of the beam axes from the plurality of
transducers in order to build up a complete cross-sectional
visualization may be provided by two alternative means. The first
means of obtaining oscillatory motion of the beam axes is by
mechanically scanning all of the plurality of transducers either
independently or simultaneously. In this case, although mechanical
movement of the transducers does introduce a limitation on the
scanning rate, the effect of this limitation may be minimised by
providing suitable switching means which require the transducers to
scan only once while obtaining a complete cross-sectional
visualization. Thus, each transducer is activated in turn to direct
a pulse of ultrasonic energy along the beam axis, the rate at which
the transducers are activated being sufficiently fast, compared
with the rate of mechanical oscillation of the transducers, that
each transducer oscillates only a small distance between successive
activations thereof. The final result achieved by this method of
operation is that at the end of a single mechanical scan, each of
the transducers has been activated whilst it's beam was directed in
all required directions. It will be apparent that monitoring of the
direction of the beam axes will be necessary in order to build up
the complete visualization.
The alternative means of obtaining oscillatory motion of the beam
axes is by use of transducer arrays at each transducer position,
the arrays being appropriately designed as to be capable of being
steered electronically. In such a system there are no moving parts
and the scanning rate obtainable with this system is limited only
by considerations of electronic switching speeds and the rate of
acquisition of ultrasonic information by the transducer after each
transmitted pulse. Since such an array may be electronically
steered to direct its beam in all required directions at a rate
much faster than that possible when mechanical oscillation of the
transducer is required, it is possible to operate this system by
steering the beam from each transducer array to each of the
required directions to measure the reflected echoes before
activating the next transducer array and steering the beam from it
to each of the required directions, and so on. It will, however, be
appreciated that this plurality of transducer arrays capable of
being electronically steered may also be operated in a manner
similar to the operation of the mechanically oscillated transducers
previously described.
In a further important aspect of the present invention, however,
the individual transducers of an array which is being mechanically
scanned may be energized in a "scattered" operation rather than in
a sequence of energizing adjacent transducers. Thus, instead of
energizing transducer No. 2 after transducer No. 1, and then
transducer No. 3, transducer No. 4 and so on, in accordance with
this invention transducer No. 5 in the array may be energized after
transducer No. 1, then transducer No. 2 followed by transducer No.
6 and so on. It has been found that such "scattered" operation of a
plurality of transducers enables even further speeding up of the
visualization since it enables one transducer to be energized
without having to wait for multiple reflections arising from
energization of the previous transducer to die down, this being
possible since the transducer is to transmit its pulse and receive
reflections along a beam which is spaced substantially from the
beam of the previous transducer. Since the "wait period" which can
be avoided by such "scattered" operation may be of the order of 500
.mu. sec, a significant speeding up of the examination is thereby
achieved.
In yet another mode of operation of the apparatus of the present
invention the individual transducers of an array may be energized
in such a manner that the time of display of echoes approximates
the total available time. In the "scattered" operation described
above in which the circuit conventionally includes a single
deflection generator circuit for the display means, the time of
display of echoes is approximately half of the total available
time, the other half of the available time being taken up by time
for transmission of the pulses through the coupling medium. In the
present alternative mode of operation, however, it has been found
that the use of two deflection generator circuits enables one pulse
to be transmitted through the coupling medium during the period of
display of echoes from the preceding pulse so that the display of
echoes from the one pulse may commence almost immediately after
conclusion of the display of echoes from the preceding pulse.
Where the plurality of transducers are mounted in a single arm in
accordance with the present invention for oscillation in the plane
of the arm, it is preferred that the transducers be mechanically
linked for simultaneous oscillation. Thus a single motor may be
utilised for oscillation of all of the transducers, and, if
desired, a single monitoring device may be utilised to monitor the
oscillation of all transducers since their respective beams will be
fixed relative to one another. In accordance with a preferred
aspect of the present invention the single arm is mounted on a
supporting mechanism which provides for both rotation and tilting
of the arm with respect to the object under examination. Rotation
of the arm of course enables different cross-sectional
visualization to be obtained without repositioning the object while
tilting of the arm enables the transducers to be directed to a
single point from different angles, thereby enabling inclined
sections to be obtained. Appropriate drive means may be provided to
perform this rotation and tilting, and monitoring means provided to
measure the position of the transducers. Similarly, drive means and
monitoring means are provided to move the arm in the "x", "y" and
"z" directions and to monitor this movement.
Other features of the present invention are illustrated in the
accompanying drawings in which:
FIGS. 1 to 3 illustrate schematically apparatus in accordance with
the present invention;
FIG. 4 illustrates in more detail the mechanism for oscillation of
the transducers of the apparatus of FIGS. 1 to 3;
FIG. 5 shows a basic block diagram of one form of the electronics
for ultrasonic examination apparatus in accordance with the present
invention;
FIG. 6 shows a transmitter and receiver switching block diagram for
the circuit of FIG. 5;
FIG. 7 shows a block diagram of an angle and origin switching
network for the circuit of FIG. 5;
FIG. 8 graphically depicts a "scattered" mode of operation of the
apparatus utilising the circuit of FIG. 5;
FIG. 9 shows a modification of the circuit of FIG. 5; and
FIG. 10 graphically depicts an alternative mode of operation of the
apparatus utilising the modified circuit of FIG. 9.
As shown in FIGS. 1 to 3 of the drawings, the apparatus of the
present invention comprises a housing 19 in the form of a couch
upon which a patient 17 can be positioned. The patient 17 is
positioned with the region to be examined placed in contact with a
flexible coupling membrane 18 which seals an aperture in the top of
the housing. Housing 19 is filled with a coupling medium such as
water and is provided with a header tank as at 24 to maintain
proper contact between the patient and the membrane.
Located within the housing 19 and immersed in the coupling medium
is a plurality of transducers 2 spatially mounted in a main
supporting arm 1 so as to be capable of oscillating in the plane of
the arm, thereby directing the respective pulses of ultrasonic
energy along beams which are steerable in said plane. Eight
transducers are shown in the FIGS. by way of example, however it
will be appreciated that this number may be increased or decreased
as desired. As shown in greater detail in FIG. 4, each transducer 2
is arranged to oscillate about pivot center 3 by action of
oscillator arm 4. The respective oscillator arms 4 of each of the
transducers 2 are coupled by links 5 which are provided with
adjusters 6 to enable accurate positioning of the transducers 2
with respect to each other and the arm 1. One of the oscillator
arms 4 is provided with a sector gear 7 which meshes with a geared
output 8 of motor 9, attached to arm 1. It will be apparent that
rotation of the shaft 8 of the motor 9 will result in simultaneous
pivoting of each of the transducers 2 about its pivot center 3. The
position or angle of each transducer is monitored by means of
monitoring potentiometers 10.
Referring again to FIG. 1, main arm 1 is mounted on a main frame
which is slidable towards and away from the patient 17 to enable
positioning of the transducers mounted on arm 1 relative to the
patient. The main frame is slidable on pillars 11 and movement
along these pillars is controlled by motor 12, for example, by
means of a rack and pinion drive. The main frame is also mounted on
a carriage 25 which slides along a track 15 controlled by motor 22
(FIG. 3), again by means of a rack and pinion drive or the like. As
depicted, the apparatus enables movement of carriage 25 along track
15 transverse to the patient 17 in the position depicted.
Longitudinal movement of the arm 1 with respect to the patient is
effected by movement along track 16 provided by motor 23 (FIG. 3)
again, for example, by means of a rack and pinion drive.
As best seen in FIG. 2, arm 1 is mounted on a frame 20 which is
supported by bearings or the like on carriage 25 for tilting motion
with respect to the patient. Thus frame 20 is provided with an
arcuate track section which engages the shaft of motor 13, for
example in a rack and pinion type drive, for tilting of the arm.
Frame 20 is in turn mounted on turntable 21 which provides rotary
motion of the arm 1 relative to the carriage 25, this rotary motion
being controlled by motor 14. It will thus be apparent that by
provision of appropriate mechanisms supporting arm 1, this arm can
be positioned transversely, longitudinally, or toward or away from
the patient. Further, the arm may be tilted or rotated relative to
the patient to enable any desired plane of scan of the transducers
2. By way of example, the arm may be rotated in increments of
1.degree. through 180.degree. to give transverse, longitudinal or
oblique echograms, and it may be tilted in increments of 1.degree.
through an angle of .+-.30.degree. to give inclined section. The
tilting movement of the arm is designed to pivot about the patients
skin line minimising the translational movement of the scanning
plane normally obtained with tilting. The arm may also be
translated in the "x", "y" and "z" directions in increments ranging
from 1 mm to 2 cm to give automatic acquisition of a number of
parallel echograms separated by the selected distance. With the
water coupling method all of these sections are obtained without
changing the coupling to the patient thus allowing reliable cross
correlation of detail in echograms obtained in different
planes.
Preferably, all movement of the transducer means is powered by
stepper motors. These have the advantage that their operation is
controlled by the application of electrical pulses. For oscillatory
motion of the transducers the rate of application is gradually
built up, then kept constant during the echogram forming period and
then gradually slowed down giving a reproducible even motion
necessary for the attainment of a consistent grey scale and
reducing the vibrations set up during acceleration of deceleration
of the transducers. Stepper motors are also amenable to control by
computers and all of the motions of the scanner may be placed under
computer control.
The rapid rate of acquisition of high quality echograms has obvious
advantages. It reduces blurring of detail caused by movement of
structures during the echogram forming period and allows quasi real
time viewing of the same section. Alternatively it allows the
taking of many views from different angles making the examination
somewhat similar to fluoroscopy. The total time necessary for the
total examination is also significantly reduced allowing the same
instrument to handle a must greater clinical load. The instrument
also has the advantage that it utilises the minimum number of
pulses to acquire a compound scan echogram and no tissue need be
irradiated more than for example eight times. To minimise the
irradiation dosage the attenuator settings of the echoscope control
the level of the transmitted energy and not the gain of the
receiver. The echoscope of this invention may also have the
provision to switch off any set of transducers and also allow a
simple scan to be obtained from any transducer.
The many degrees of movement of the apparatus of this invention
makes it very versatile and it can be used in a variety of other
modes of operation. For instance by combining a translational
movement in the length direction of the arm, a compound scan
echogram is obtained where the origin of oscillation of the
transducers is moved. This mode of operation is useful in
circumstances where it is desirable to view around some overlying
shadowing structures such as ribs. This translation movement also
reduces the Moires interference pattern obtained in the stationary
mode of operation. The translation movement in this case need not
be large, a movement corresponding to the inter transducer distance
being adequate and this movement may be achieved in the same time
as that taken for the single oscillatory movement.
In another mode of operation all of the transducers may be made to
function as a single transducer corresponding to the size of the
arm, and focusing techniques of the type used in annular phased
array transducers may be used to generate a highly focused line of
sight along the axis of the arm. A linear scan may then be formed
by translating the arm in the length direction.
The multiple transducer configuration of the echoscope may be used
to examine tissues in the single transmit-multi receiver mode of
operation analogous to the multi-channel receiver operation used in
seismology. Cross-correlation of information received by the
multiple transducer may then be used to reduce multiple reflection
artifacts in tissue and to measure local values of velocity in the
various visualised tissues.
The echo scattering cross-section of tissue may also be obtained by
two methods with the echoscope. In the first method, the tilting
motion of the echoscope is used, the echo scattering cross-section
being obtained from tissue at a depth corresponding to the
projection from the transducer to the axis of rotation of the
tilting motion. For a transducer facing vertically up this depth is
equal to the radius of curvature of the tilting motion.
Alternatively, by pointing the transducers to cross at the center,
the echo scattering cross-section of tissue lying at the radius of
curvature of the arm may be obtained by rotating the arm. The first
method gives the echo scattering cross as a function of the angle
in a fixed plane while the second method gives the value of this
parameter when viewed at constant angle in a variable plane. In
both methods the multiple transducer nature of the echoscope also
allows a relatively coarse two dimensional dependence of the
parameter.
One mode of operation of the apparatus in accordance with this
invention is depicted in FIGS. 5 to 7.
As shown in FIG. 5, the master clock 65 provides basic time
impulses to initiate multi-channel clock 64 and to drive motors 52,
54 via the motor controller 57, 58, 59.
The multi-channel clock 64 outputs, in turn, trigger pulses to each
channel upon receiving a pulse from the master clock 65.
The channel selector 60 counts trigger pulses and sends a binary
channel address code to transmitter and receiver switching network
55 and to angle and origin switching network 56.
The signal processor 62 processes echoes from transmitter and
receiver switching network 55, which echo signals are fed together
with blanking pulses to the intensity modulation input of the
display unit 66.
Deflection generator 61 generates X and Y deflection voltages from
signals received from angle and origin switching network 56.
FIG. 6 shows the transmitter and receiver switching network in
greater detail. As seen in FIG. 6, transmit and receive decoder 73
decodes channel selector output signals from channel selector 60 to
activate the correct diode switch drive 72 and transmitter drive
71. The multi-channel clock output then triggers the transmitter
drive 71 to energize the transmitter 70.
Receiver diode switch 74 is energized by the decoder 73 via diode
switch drive 72 which allows echo signals to pass to the
preamplifier 76.
In FIG. 7, the angle and origin switching network 56 of FIG. 5 is
more fully disclosed. As seen in FIG. 7, angle and origin decoder
82 decodes the channel selector output to activate the correct
switch drive 81 and hence turn on the correct potentiometer supply
switch 80. The supply switch 80 supplies reference voltages to the
sine cosine angle monitoring potentiometer 83 and to the origin
network 84.
The X and Y origin coordinates from the origin network 84 and the
sine and cosine angle output from the potentiometer 83 are fed via
their respective OR gates to the deflection generators 61 (see FIG.
5) within the processing electronics.
FIG. 8 illustrates graphically the "scattered" mode of operation
which can be adopted using the circuits of FIGS. 5 to 7. It will be
apparent from FIG. 8 that by timing the pulses such that pulse 1 is
followed by pulse 5, rather than directly by pulse 2, pulse 5 may
be transmitted through the water acting as the coupling medium
after a brief lapse of time, the settling time, following
completion of the display of echoes from pulse 1. As described
above, in this "scattered" mode of operation, transmission of pulse
5 through the coupling medium need not be delayed until multiple
reflections from pulse 1 die down as the beam of pulse 5 is
substantially spaced from the beam of pulse 1. Of course, when
pulse 2 is transmitted after the display of echoes from pulse 5 and
a brief settling time the multiple reflections from pulse 1 will by
then have died down. FIG. 8 illustrates that by use of this mode of
operation a display time approximating half the total available
time can be achieved.
FIG. 9 shows a modification of the circuit of FIG. 5 in which
deflection generator 61 thereof is replaced by deflection generator
1, deflection generator 2 and a deflection selector. Separate angle
and origin switching networks are also provided for each deflection
generator. Other integers of FIG. 9 which are not shown are as
shown in FIG. 5.
FIG. 10 illustrates an alternative mode of operation of the
apparatus of the present invention, utilising the modified circuit
of FIG. 9. In this alternative mode of operation, the existence of
a second deflection generator enables pulse 5 to be transmitted
through the coupling medium at substantially the same time as the
display of echoes from pulse 1 is effected using the first
deflection generator. Thus, display of echoes from pulse 5 can be
effected almost immediately after completion of display of echoes
from pulse 1. At substantially the same time, pulse 2 can be
transmitted through the coupling medium utilising the first
deflection generator. FIG. 10 illustrates that by use of this mode
of operation a display time approximating the total available time
can be achieved.
From the foregoing description it will therefore be appreciated
that the present invention enables more rapid and complete scanning
of an object subject to ultrasonic examination. While the invention
has been described with reference to illustrative embodiments, it
will be generally understood by those skilled in the art that
various changes may be made and equivalents be substituted for
elements thereof without departing from the true spirit and scope
of the invention.
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